The invention relates to an apparatus for applying a thin liquid film of large width to a continuously moving web of material, comprising a liquid supply chamber which is fed by a pump and a guide surface which is supplied from the liquid supply chamber and from the edge of which a liquid film runs onto the web of material.
For applying a thin liquid film to a continuously moving web of material, it is known to convey a liquid film by means of a roll from a liquor trough and to remove said film from the roll by means of a doctor, the film then passing from said doctor to the web of material. However, this generally requires a thickening agent to obtain satisfactory film formation on the roll. This then requires subsequent washing of the web of material to remove the thickening agent.
It is further known to immerse a roll in a liquid supply container which is fed from a pump with the liquor and comprises an overflow weir, said roll being disposed adjacent the overflow weir and serving primarily to break the waves caused by the liquor supply. In this construction a relatively large volume is required for the liquid supply container so that the conveying impulses originating from the pump have the least possible effect at the guide surface following the overflow weir. A large volume of the liquid supply container involves however considerable practical disadvantages, as should be readily obvious (for example, the losses when changing the colour).